2)To reach an absolute pressure of 3atm, you must dive down (in water) to depth of approximately 20m. Why might someone think that the answer was 30m

Someone might think the answer is 30 m when the person cannot distinguish between absolute pressure and gauge pressure.

Explanation:

Given absolute pressure at a depth of 20 m = 3 atm.

When you drive down 30 m in water, the gauge pressure experienced is calculated as;

P = ρgh

Where;

ρ is density of water = 1000 kg/m³

g is acceleration due to gravity, = 9.8 m/s²

h is the depth of water = 30 m

P = (1000)(9.8)(30)

P = 294000 Pa

in atm = ≅ 3 atm.

Thus, someone might think the answer is 30 m when the person cannot distinguish between absolute pressure and gauge pressure.

c. newton's third law of motion

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.